Experimental studies of microwave amplification in the ion-focusedregime

Studies of microwave amplification with an in-focused electron beam drawn from an induction injector are reported. A free-electron laser (FEL) operating at 9.4 GHz and employing ion-focusing within the interaction region has achieved power in excess of 30 MW at 9.4 GHz, with a beam energy of 0.8 MeV and current of 0.7 kA. Peak gain is 20 dB/m, with no saturation after 15 wiggler periods. Also reported are the first evolution and detuning data for an ion-channel laser/maser (ICL). Two shortcomings of the prematurely halted ICL studies are poor frequency discrimination and a large axial plasma gradient. Prospects for operation with an upgraded 1.6 MeV accelerator are discussed     

Collaborative monitoring study of airborne particulate matters among seven Asian countries

Summary Seven Asian countries have been collaborating in collecting airborne particulate matter (APM) in their individual countries and analyzing them by neutron activation analysis as a common analytical tool. APM samples were collected into two fractions of fine and coarse grains (PM2 and PM2-10, respectively). Analytical data were compared from several viewpoints such as particulate sizes, locality of sampling sites (either urban or rural) and geographical location of participating countries. Chemical composition and their monthly variations as well as mass concentrations appear to be highly characteristic for individual sampling sites, suggesting that NAA data are suitable for evaluating the air quality in each site.     

Synthesis of pyridinium ylide complexes of methylcobaloxime and crystal structure determination of [benzoyl(1-pyridinio)methanide]bis(dimethylglyoximato)methylcobalt benzene solvate

Summary Pyridinium ylide complexes of methylcobaloxime were synthesized by the treatment of an ylide with Co(Hdmg)₂ Me(SMe₂). The crystal structure of one of the complexes, [Co(Hdmg)₂Me C₅H₅NCHCOPh]C₆H₆ has been determined by x-ray diffraction techniques. The crystals are monoclinic, space group P2₁/c, witha = 10.456(5),b = 11.079(4),c = 24.58(1) Å, = 99.58(6), V = 2808 ų, Z = 4. The Co-C (ylide) bond distance is 2.18 Å and Co-C(methyl) 2.04 Å. C(ylide)-Co-C(methyl) bond angle is 174.9°. The crystal, i.r. and¹H n.m.r. data suggest that thetrans-influence of the ylide ligands is larger than that of py, Melm, OH₂ or PPh₃.     

Optimal laser control of ultrafast photodissociation of I2- in water: mixed quantum/classical molecular dynamics simulation

A linearized optimal control method in combination with mixed quantum/classical molecular dynamics simulation is used for numerically investigating the possibility of controlling photodissociation wave packets of I(2)(-) in water. Optimal pulses are designed using an ensemble of photodissociation samples, aiming at the creation of localized dissociation wave packets. Numerical results clearly show the effectiveness of the control although the control achievement is reduced with an increase in the internuclear distance associated with a target region. We introduce effective optimal pulses that are designed using a statistically averaged effective dissociation potential, and show that they semiquantitatively reproduce the control achievements calculated by using optimal pulses. The control mechanisms are interpreted from the time- and frequency-resolved spectra of the effective optimal pulses.     

How Effectively is the Photon Activation Analysis Applied to Meteorite Samples?

Chondritic meteorite samples were analyzed nondestructively by photon activation analysis. Powdered samples weighing about 50 mg each were irradiated with photons (-rays) converted from electrons accelerated by a linear electron accelerator at 20 and 30 MeV. With 30-minute and 6-hour irradiations, 11 and 12 elements with duplication of 6 elements could be determined, respectively. Considering that several major elements including Mg, Si and Fe can be determined in addition to Ti, Rb, Sr, Y and Zr, which cannot or hardly be determined by instrumental neutron activation analysis (INAA) with rather high sensitivity, instrumental photon activation analysis is as effective as INAA.     

Optimal control of ultrafast cis-trans photoisomerization of retinal in rhodopsin via a conical intersection

Optimal control simulation is applied to the cis-trans photoisomerization of retinal in rhodopsin within a two-dimensional, two-electronic-state model with a conical intersection [S. Hahn and G. Stock, J. Phys. Chem. B 104, 1146 (2000)]. For this case study, we investigate coherent control mechanisms, in which laser pulses work cooperatively with a conical intersection that acts as a "wave-packet cannon." Optimally designed pulses largely consist of shaping subpulses that prepare a wave packet, which is localized along a reaction coordinate and has little energy in the coupling mode, through multiple electronic transitions. This shaping process is shown to be essential for achieving a high target yield although the envelopes of the calculated pulses depend on the local topography of the potential-energy surfaces around the conical intersection and the choice of target. The control mechanisms are analyzed by considering the motion of reduced wave packets in a nuclear configuration space as well as by snapshots of probability current-density maps.     

Fragmentation of the metastable molecular ion of methyl lactate: The formation of oxygen-protonated methanol [CH3OH2]+ involving double hydrogen atom transfers

The spontaneous unimolecular dissociation reaction of methyl lactate (1) ionized by electron impact was investigated by a combination of mass-analyzed ion kinetic energy spectrometry and deuterium labeling. The metastable ions 1^+· decompose in a variety of ways: four fragment peaks are observed at m/z 89, 76, 61, and 45, which correspond to the losses of ?H₃, CO, CH₃?O, and ?OOCH₃, respectively. Double hydrogen atom transfer occurs in the third reaction. The source-generated m/z 61 ions decompose into oxygen-protonated methanols at m/z 33 ([CH₃OH ₂ ⁺ ]) by the loss of CO with double hydrogen atom migration. Both hydroxyl and methyne hydrogen atoms in 1 ^+· are present in the resultant protonated methanols.     

Photoinduced graft polymerization of 2-methacryloyloxyethyl phosphorylcholine on polyethylene membrane surface for obtaining blood cell adhesion resistance

Phospholipid polymer, poly[2-methacryloyloxyethyl phosphorylcholine (MPC)], was grafted with polyethylene (PE) membrane using photoinduced polymerization technique to make the membrane resistant to cell adhesion. The water contact angle on the PE membrane grafted with poly(MPC) decreased with an increase in the photopolymerization time. This decrease corresponded to the increase in the amount of poly(MPC) grafted on the PE surface. The same graft polymerization procedure was applied using other hydrophilic monomers, such as acrylamide (AAm), N-vinylpyrrolidone (VPy) and methacryloyl poly(ethylene glycol) (MPEG). These monomers were also polymerized to form grafted chains on the PE membrane, and the grafting was confirmed with X-ray photoelectron spectroscopy. Analysis of amount and distribution of plasma proteins at the plasma-contacting surface of the original and the modified PE membranes were analyzed using immunogold assay. The grafting of poly(MPC) and poly(VPy) on PE membrane reduced the plasma protein adsorption significantly compared with that on the original PE membrane. However, the PE membranes grafted with poly(AAm) or poly(MPEG) did not show any effects on protein adsorption. Platelet adhesion on the original and modified PE membranes from platelet-rich plasma was also examined. A large number of platelets adhered and activated on the original PE membrane. Grafting with poly(AAm) did not suppress platelet adhesion, but grafting with poly(MPC) or poly(VPy) on the PE membrane was effective in preventing platelet adhesion. It is concluded that the introduction of the phosphorylcholine group on the surface could decrease the cell adhesion to substrate polymer.     

Non-destructive elemental analysis of large meteorite samples by prompt gamma-ray neutron activation analysis with the internal mono-standard method

Prompt gamma-ray neutron activation analysis (PGNAA) using the internal mono-standard method was tested for its applicability to analyzing large solid samples including irregularly shaped meteorite samples. For evaluating the accuracy and precision of the method, large quantities of the Geological Survey of Japan standardized rock powders (JB-1a, JG-1a, and JP-1) were analyzed and 12 elements (B, Na, Mg, Al, Cl, K, Ca, Ti, Mn, Fe, Sm, and Gd) were determined by using Si as an internal standard element. Analytical results were mostly in agreement with literature values within 10 %. The precision of the method was also shown to be within 10 % (1σ) for most of these elements. The analytical procedure was then applied to four stony meteorites (Allende, Kimble County, Leedey, Lake Labyrinth) and four iron meteorites (Canyon Diablo, Toluca (Mexico), Toluca (Xiquipilco), Squaw Creek) consisting of large chunks or single slabs. For stony meteorites, major elements (Mg, Al, Si, S, Ca, and Ni), minor elements (Na and Mn) and trace element (B, Cl, K, Ti, Co, and Sm) were determined with adequate accuracy. For iron meteorites, results for the Co and Ni mass fractions determined are all consistent with corresponding literature values. After the analysis, it was confirmed that the residual radioactivity remaining in the sample after PGNAA was very low and decreased down to the background level. This study shows that PGNAA with the internal mono-standard method is highly practical for determining the elemental composition of large, irregularly shaped solid samples including meteorites.